A week from today, barring a last-minute upset, there will be a small, quiet signing ceremony, probably in Strasbourg. Not even the UK Foreign Office seems entirely sure of the venue or its format. But no one is questioning the scale of the ambition nor the risks which underpin this event - the opening of the accession process for Turkey's membership of the European Union. Welcome to regime change, European-style.

The parallels are inescapable: the US launched its regime change in a Muslim country with shock and awe, an unprecedented onslaught of military power. The EU quietly initiates its regime change in the Muslim country next door with the shock of 80,000 pages of EU regulations on everything from the treatment of waste water to the protection of Kurdish-minority rights. While one sends in its Humvees and helicopters, the other sends in an army of management consultants, human-rights lawyers and food-hygiene specialists.

The more the US model of regime change disintegrates into violent chaos in Iraq, the more the EU glows with discreet pride in its own unparalleled record of successful regime change, from post-dictatorship Spain and Portugal to the more recent enlargement countries such as Hungary and Estonia.

The EU model uses the incentive of membership to insist on dramatic change - once a country is a member, the leverage is lost. So Turkey will have to jump through a number of hoops on issues such as corruption and sewerage, which might trip up many of the oldest EU members. It's a style of regime change which is "cheap, voluntary and hence long-lasting", points out Steven Everts in a new pamphlet,Why Europe Should Embrace Turkey.

This kind of regime change is the only way in which the EU can lay claim to being a serious global player - on almost every recent international crisis, from Bosnia to Iraq, internal squabbles crippled an effective response. No wonder then that there are plenty of Europhiles, particularly in the UK, whose eyes glitter at the prospect of Turkey in the EU queue. They rattle off the long list of advantages: the geostrategic significance of Turkey in relation to the Caucasus and the Middle East; the key gas supplies that now run through Turkey; the demographic advantages of a much younger population; the dynamic Turkish economy - grown by a quarter since 2001; securing Europe's back door against drugs and people-trafficking.

Besides, Turkey has aspired to EU membership for over 40 years, and such has been its enthusiasm in the past few years that, to win Brussels' favour, it has agreed to the most ambitious political and economic reform programme since the great secular moderniser Kemal Ataturk. Regime change is already well under way in Istanbul, but not irrevocable; the prospective trial of the novelist Orhan Pamuk for his comments on the Armenian massacre indicate that some in Turkey are only too keen to torpedo the whole process. If Europe was to turn truculent with Turkey, an extraordinary opportunity to strengthen human rights and ensure stable democracy would be lost. The conclusion is clear: Turkish membership is a "no-brainer", insist Britain's Euro elite - commentators, government and analysts alike.

What fuels this British enthusiasm is that Turkey offers the tantalising possibility of exorcising the "clash of civilisations" ghost. If there was a secular, democratic, economically successful Muslim state it would kill off intense arguments about the incompatibility of Islam with democracy or Islam with human rights and modernity. Furthermore, 80 million Turks within the EU would also kill off the EU's credibility deficit in the Muslim world, where it's seen as a Christian, white club with a dodgy imperial past (although the latter is as much a Turkish problem as a European one in the region). Finally - the coup de grace - it would strengthen the claim of Europe's 15 million-strong Muslim minority to a home in Europe. In sharp contrast to the US, Europe could shape a new, prosperous and peaceful accommodation between Islam and the secular west.

But this is the nub of the problem - vast swaths of Europe don't buy it. Either they don't believe a peaceful accommodation with Muslims is possible or they fear it requires such a dilution of European identity that they don't want it. Britain's enthusiasm is echoed in only a few countries such as Poland and Spain, while across the rest of the continent the "clash of civilisations" argument is flourishing. Hence the quietness of the short ceremony next Monday. No one has any desire to launch this project of regime change with a fanfare - it fills European populations with horror. The figures from a recent Eurobarometer poll tell it all: 80% of Austrians are against, and only 10% in favour; 70% of the French are against and 74% of the Germans. It's going to need a very hard sell to convince millions of people that Turkish membership is in their interests, and after the failure of a previous Euro elite project - the constitution - no one's relishing the challenge.

The accession process will take at least a decade and over that time both the EU and Turkey are likely to change dramatically, but what will make the process so fascinating is that as the rows rumble on (no one denies that it's going to be rocky - the Turks are allegedly "terrible negotiators", every detail becoming a point of national honour) it will be the canvas on which will be projected all of Europe's crucial choices.

Will self-interest - put crudely, young Turks might pay for ageing Europe's pensions - be trumped by the unpredictable politics of identity as an insecure Europe, aware of its shrinking demographic and economic weight in the world, pulls up the drawbridge and opts to define itself more narrowly around its historical Christian identity?

This self-interest isn't obvious: it will need European politicians to do a lot of explaining. Geostrategic thinking doesn't come easily to your average voter and they'll need reassurance that they are not going to be swamped by cheap Turkish labour. Free movement of labour can be staggered, as it is for the new eastern European members, and is unlikely to come before 2022. Similarly, structural funds are not going to be swallowed up whole in the peasant hinterland of Anatolia and probably won't be accessible by Turkey until after 2020.

But the reticence about taking on the advocacy role for Turkish membership has been evident across the political spectrum in Germany as politicians fear being ambushed by the visceral emotions stirred up by Turkey. Austria and Germany are still thinking of the geese whose honking woke the army when Vienna was under siege from the Ottoman Turks in the 16th century, commented one seasoned observer.

Can such history be laid to rest when it has sunk such long and deep roots into the national identity? All over the world, in places such as Rwanda and South Africa, there are many grappling with different formulations of just that question. The EU ploughs funds and diplomacy in to achieve an affirmative. How hollow does that ring if Europe itself, despite all its vaunted values of freedom and tolerance and its envied prosperity, fails the test and lets history win. Watch Turkey's accession process in the years to come as the barometer of Europe's degree of civilisation.